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Vertical hit and miss engine

I've caught up on all of my summer chores, and the weather outside is cold and rainy and horrible. I have been bored this week, and when I get bored, I start to design things. I have watched enough YouTube videos of Bob Shores Silver Angel to suss out the hit and miss mechanism, and I am impressed by it. I have ordered a set of 2:1 bevel gears off Ebay and I'm waiting for them to arrive. This engine will have a bore and stroke of 1", and a single flywheel. It will have an oil sump, and the same general configuration as the Angel. I will be using my most current carburetor design (without the offset in the carb body). The valves will be my standard 1/8" stem and 3/8" head. Sparkplug will be a 10 mm CM6 from NGK because they are available at autoparts stores. Probably as the design progresses I will support the horizontal gas tank on a pair of stand-offs from the engine. I do plan on building this engine, but it will take a backseat to other summer things and impending eye surgery in July. This will give me an engine to run my face cam on. Follow along. it should be fun.---Brian

I'm going to go with a couple of heavier ball bearings this time. The bearings I have been using are only .906" diameter x 5/16" thick. They get the job done, but I think they are a bit too light, especially with the weight of the flywheels. My new larger bearings are 3/8" i.d. x 1 1/8" o.d. x 3/8" thick. There is not a huge price difference, and I think I'll be a bit happier with them. I haven't modelled in the gears yet, as I haven't received them yet. When I do receive them I will model them and insert them into the 3D assembly. These will not be helical gears like I used in my last two builds, but will be bevel gears. You will also notice that the flywheel is not symmetrical about it's centerline. The ignition points and cam will fit on that side of the engine, and I don't want the flywheel to stick out a long ways from the center of the engine to clear them. By making the flywheel non symmetrical I can fit it in much closer to the engine.

Dan, I don't have the faintest idea. The output of any of these small engines is fractional horsepower, and I have never measured it nor even wondered about it. For me, the biggest success is that they run well.--Brian

Have you ever measured the BHP of any of your engines? Any estimates of what this one will have?

I second this motion. A little prony brake acting on a digital kitchen scale could be employed https://en.wikipedia.org/wiki/Prony_brake. If you can borrow a tach off your mill or lathe, watts will be your reward, and ours.

Today I ordered the aluminum to build the crankcase and two side-plates for the engine. All will be cut from 4" diameter round stock. None of these parts will be terribly difficult to make as individual pieces. The difficult part will be to have all of the outer surfaces line up perfectly. The holes in the center of the two outer plates will be 13/32" thru, to give clearance for the 3/8" crankshaft. The center hole in the main body will be 2.3" in diameter to allow for the swing of the crankshaft and big end of the rod. The side-plate on the flywheel side will have two tapped holes which will hold the ignition points. The other side will have two tapped holes for the camshaft support bracket. My plan at the moment (and that may change) is to put the three individual pieces up in the 3 jaw chuck and drill and ream the center holes in all three pieces to 13/32", then make up a 13/32" shoulder bolt long enough to pass thru all three pieces, and clamp them all together with a hex nut on the shoulder bolt. I will need one more bolt thru each side-plate, leading to tapped holes in the main body plate to act as an anti rotation device. I will then bandsaw and mill all three plates locked together to the final outside dimensions. After that, separate the three plates and set the main center body up in the four jaw, pick up on the reamed center hole to find exact center, then bore the hole out to 2.3". The counterbored bolt holes in the outer plates and the tapped holes for them in the center main body can be put in after the fact.

So--There we have 95% of the material required to build this engine. The three pieces of 4" dia. aluminum which will become the main center body and the two side plates, the flatbar to make the "feet", and the 4 1/2" diameter piece of 1018 round stock that will become the flywheel. That cost me $30, and the two new bearings cost $20.

At the last moment I decided not to machine things as I had shown in an earlier post. With the main body held in the 3 jaw chuck I faced the exposed side, then drilled and bored the center hole in one set-up. Then I flipped it around 180 degrees in the 3 jaw, made sure that the previously "faced" side was up tight against the jaws, and faced the other side. the sideplates both have a "register diameter" that will fit into this hole in the main center piece.